JPH11320214A - Covered hard tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a covered tool which can enhance the tight attachment, toughness, etc., of the oxide covering formed through a physical evaporation method and improve remarkably the tight attachment of a skin film containing oxygen. SOLUTION: A covered hard tool is formed by forming a hard covering layer by the ion plating method and is based upon a super-hard alloy such as high-speed steel, super-hard alloy, thermet, wherein at least part of the covering layer is formed by alternately laminating the first layer expressed by (Tix Al1-x )N, where 0.2<=x<=0.5, and the second layer expressed by (Tix Al1-x ) Oy N1-y , where 0.5<=x<=0.7 and 0.01<=y<=0.5, and the second layer is configured so that the first layer in contact thereto is continued to the crystals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated hard tool having excellent oxidation resistance of a film and, as a result, excellent wear resistance.

[0002]

2. Description of the Related Art Conventionally, TiN,
Although coatings such as TiCN have been used widely and generally, recently, Japanese Patent Publication No. 4-53642 and Japanese Patent Publication No.
As typified by Japanese Patent Publication No. 5 (1993), studies have been made on adding Al. In these studies, the purpose is to improve the oxidation resistance and wear resistance of the film by adding Al to the film. However, recently the cutting speed has tended to be even higher, and the case of cutting hardened steel after heat treatment has also been increasing. In such a case, the cutting edge temperature of the tool becomes extremely high, and simply adding Al At present, it is no longer possible to obtain sufficient oxidation resistance enough to withstand use.

[0003] On the other hand, it has been proposed to coat the outermost layer with TiAlON or the like in order to further improve the oxidation resistance (Japanese Patent Laid-Open No. 7-328811), but sufficient oxidation resistance can be obtained with an oxide of Ti and Al. Has not been reached. Although a proposal has been made to coat the outermost layer with alumina (Japanese Patent Application Laid-Open No. Hei 9-192906), the alumina coating in ion plating has weak adhesion itself and is easily peeled off, so that in actual cutting, an impact force is applied. Therefore, it can be said that it is not satisfactory yet.

[0004]

According to the study of the present inventors, in a TiAlN film in which Al is added to Ti, the oxidation start temperature in the atmosphere is improved with respect to 450 ° C. of TiN, and the amount of Al added is reduced. 750 ° C to 900 ° C as the temperature increases
To rise. However, in recent high-speed cutting and high-hardness material cutting, the cutting edge temperature often exceeds 900 ° C., and a sufficient cutting life cannot be obtained by simply adding Al. Therefore, even in such high-speed cutting, it is necessary to further increase the oxidation resistance of the film in order to realize long-life and stable cutting.

[0005]

Means for Solving the Problems The present inventors have found that peeling of a film,
As a result of intensive research on how to prevent the occurrence of sudden and catastrophic damage such as self-destruction and micro-chipping and improve the oxidation resistance of the film, the TiAlN layer as the first layer was obtained. Oxygen resistance is remarkably improved by alternately stacking and coating a second layer TiAlON in which a part of nitrogen of the first layer is replaced with oxygen and the ratio of Al to Ti is higher than that of the first layer. I came to confirm that it would. Further, the outermost layer has Al
Oxidation resistance is further improved by coating the O layer, and furthermore, oxidation resistance of each layer is improved by adding Si or a 3a group component to the outermost layer, the first layer, and the second layer, It has been found that the oxidation resistance of the entire film is further improved.

[0006]

When the mechanism of oxidation is studied using a TiAlN layer, which is said to be excellent in oxidation resistance, as an example, it was found that Al near the surface of the film diffused to the outermost surface and formed alumina, whereupon oxidation started. The formation of this alumina suppresses the diffusion of oxygen into the inside of the film and improves the oxidation resistance. In this case, the film immediately below the formed alumina has a rutile structure in which Al does not exist as a result of Al diffusing to the outermost surface.
It becomes i-oxide. This oxide of Ti is easily peeled off porous, and even if alumina is formed on the outermost surface, which functions as a barrier for the internal diffusion of oxygen, it is not expected that a remarkable improvement in oxidation resistance will be obtained.

[0007] Therefore, TiA is provided between the first layer of TiAlN.
When a laminated structure is formed with a second layer of ION interposed, one layer of the first layer is oxidized as described above, and even if the first layer is separated from the porous Ti oxide layer, TiA which forms the outermost layer there is formed.
Since the second layer of ION functions as a barrier for oxygen diffusion, oxidation of the film is greatly suppressed particularly in dynamic cutting, and stable long life is achieved in cutting. Of course, the TiAlON film also wears out during cutting, but since the underlying TIALON film functions similarly, the oxidation resistance of the entire film is greatly improved. Therefore, the second AlO layer is as much as possible, preferably 5
It is possible to achieve a sufficiently satisfactory cutting life by interposing more than one layer.

In addition, the second layer forms continuity of the crystal structure with the first layer, so that the adhesion is remarkably improved, and peeling during cutting does not occur. That is, for example, when the first layer has an fcc structure, the second layer is a TiAlON layer having a similar fcc structure, which fulfills the gist of the present invention. As is well known, the TiAlN layer has an fcc crystal structure under normal PVD coating conditions when the Al / Ti atomic ratio is 7/3 or less. Shows good tool properties. Further, when the atomic ratio exceeds about 7/3, no fcc structure is formed, and as the atomic ratio decreases, the hardness decreases and the toughness improves. On the contrary, as the atomic ratio increases, the hardness increases. It is well known that the oxidation resistance is improved. Furthermore, according to the results of intensive studies by the inventors, it has been confirmed that almost the same tendency is exhibited when oxygen is added to TiAlN. That is, when the atomic ratio is 7/3 or less, an fcc structure is formed, and the higher the atomic ratio is within the range of 7/3 or less, the better the oxidation resistance becomes.

From the above findings, the first layer has as high a toughness as possible without losing the abrasion resistance, the second layer has as high an oxidation resistance as possible, and the first layer and the second layer Were alternately laminated, and the same fcc structure was used to prevent peeling between the films so that continuity of the crystal was obtained.
Here, the Al / Ti ratio of the first layer TiAlN is 2/8 to
Setting to the range of 5/5 is in accordance with the gist of the present invention, and 2
If it is less than / 8, the abrasion resistance decreases, and if it exceeds 5/5, the toughness becomes insufficient. In addition, Al /
Setting the Ti ratio in the range of 5/5 to 7/3 satisfies the gist of the present invention. If the Ti ratio is less than 5/5, the oxidation resistance becomes insufficient.
If it exceeds 7/3, the fcc structure will not be obtained unless a superlattice structure is formed by forming an ultrathin film, and continuity of crystals cannot be expected. Further, the reason why the nitrogen substitution amount of oxygen is set to 0.1 to 0.5 is that if it is less than that, sufficient oxidation resistance cannot be exhibited, and if it exceeds 0.5, the toughness is reduced and it cannot be used practically. It is. The thickness of one of the second layers is 2 nm to 100 n
The reason for limiting to m is that, as a result of experiments, it has been found that if it is less than this, the effect as an oxidation-resistant barrier is insufficient, and if it exceeds this, peeling is likely to occur.

Furthermore, by providing an AlO layer as the outermost layer, the oxidation resistance in the initial stage of cutting can be improved,
The welding resistance to the workpiece is also improved, and a longer life in cutting can be achieved. In this case, the outermost layer of AlO
When the layer has an amorphous crystal structure, a further improvement in oxidation resistance is observed. That is, since oxygen diffuses preferentially at the grain boundaries, it is considered that an amorphous layer having no grain boundaries further suppresses the diffusion of oxygen and is effective in improving oxidation resistance. Further, the outermost AlO layer has γ, κ, θ, α
In the case of using such a crystalline material, although the oxidation resistance is slightly deteriorated, it is preferable to select an amorphous layer or a crystal depending on the cutting application in order to harden the AlO layer itself and improve the wear resistance. The crystal form of the AlO layer mainly depends on the deposition temperature, and is amorphous, γ, θ, κ, α
Structure. Since the AlO layer is an insulating layer, it is preferable to use a pulse bias when covering by 100 nm or more by the ion plating method.

[0011] Further, in order to improve the oxidation resistance of the first film, addition of various third components was attempted. As a result, in the addition of Y, Nd, Sm, and Sc of Si and Group 3a metals,
As a result, the oxidation resistance of the coating was significantly improved. The present inventors have found that these components segregate at the crystal grain boundaries of the first film, suppress the diffusion of oxygen at the grain boundaries, and improve the oxidation resistance of the film. The replacement amount of the third component is 1
If the content is less than atomic%, there is no effect in improving the oxidation resistance, and if the content exceeds 30 atomic%, the abrasion resistance of the film is deteriorated. Hereinafter, the present invention will be described based on examples.

[0012]

EXAMPLES Example 1 Coatings of the present invention and comparative examples were coated using three types of targets using a small-sized arc ion plating apparatus, and a coated carbide end mill was prototyped. Coating conditions were bias voltage -300V, reaction gas pressure 4 × 1.
It was set to 0 ^-2 mbar. Since the total film thickness was 2.5 μm, the total number of layers in the entire film was different in each of the examples of the present invention. The second layer and the outermost layer were formed by intermittently introducing oxygen gas. In Table 1, AlO having no particular crystal structure has an amorphous structure.

[0013]

[Table 1]

Next, an oxidation test was performed in the atmosphere at 1000 ° C. for 30 minutes to measure the thickness of the oxide layer. Table 2 also shows the results. A cutting test was performed with the obtained end mill under the following cutting conditions, and cutting was performed until breakage occurred. Table 2 also shows the cutting length at the time when the breakage occurred. End mill is φ
The work material SKD11 (HRC6
0), cutting speed 40m / min, feed amount 0.06mm /
Blade, cutting depth 12mm x 0.8mm, no cutting oil (d
ry).

[0015]

[Table 2]

As shown in Table 2, with respect to the oxidation resistance, in the case of a sample coated with oxygen or containing an oxide, the nitride layer of the first layer is hardly oxidized although it is affected by heat. It was found that the oxidation to seldom progressed. In addition, when cutting heat and rubbing wear are applied in cutting of a hardened material hardened by an end mill, the denseness of the film is maintained, so that the wear resistance is dramatically improved to 3 to 5 times.

Example 2 The same coatings of the present invention and the comparative example shown in Example 1 were coated on a cemented carbide drill and a cemented carbide insert, and a cutting test was performed under the following conditions. The drill diameter is φ6mm (JI
SP30), work material SCM440 (annealed material), cutting speed 100 m / min, feed amount 0.1 mm / rev,
Table 2 shows the amount of wear after drilling a hole having a depth of 15 mm and cutting 3000 holes. For indexable inserts,
The flank wear after 10 m cutting was measured. The cutting specifications of the insert are chip shape SEE42TN (JIS P4
0), work material SKD61 (HRC42), width 10
0mm x 250mm length chamfer, cutting speed 150m /
min, the feed amount is 0.15 m / blade, and the cut amount is 1.5 mm. Table 3 also shows the results.

[0018]

[Table 3]

As apparent from Table 3. It has been confirmed that the present invention examples also show excellent tool life for drills and inserts. The tendency is the same for end mills, drills and inserts.

Example 3 Using a small arc ion plating apparatus, a cemented carbide end mill and a cemented carbide insert coated with the present invention were produced. For the crystallization of the outermost layer, the film was formed under the coating conditions of 790 ° C. for α and 680 ° C. for γ. The cutting examples of the present invention and the comparative examples were evaluated for cutting under the cutting conditions shown in Examples 1 and 2, and the results are shown in Table 3. Also,
An oxidation test was performed at 1,000 ° C. in air for 2 hours, and the thickness of the formed oxide layer is also shown in Table 4. still,
Also in this example, the total film thickness was set to 2.5 μm.

[0021]

[Table 4]

As shown in Table 4, it is apparent that the multilayer film of the present invention exhibits better oxidation resistance and cutting life. It is clear that the oxidation resistance and tool life are further improved by interposing an oxide film inside.

Example 4 Using a TiAlX alloy target containing a predetermined amount of the third component X, a cemented carbide end mill coated with an example of the present invention shown in Table 5 was prepared, and the same cutting evaluation and example as in Example 1 were made. The same oxidation test as in Example 3 was performed. The results are shown in Table 4. In this case, the second layer is fcc AlO (2n
m) and the outermost layer was unified to an amorphous AlO layer.

[0024]

[Table 5]

From Table 4, it is clear that the third component further improves the oxidation resistance and the cutting life.

[0026]

The present invention has excellent oxidation resistance by laminating a target having a different Al content and a layer having a different oxygen content than a gas system, and has a superior effect when used as a cutting tool. Used as a long-lasting tool, especially A
Since the oxygen content can be increased by changing the amount of l, various tools that require wear resistance and heat resistance, such as cutting tools such as turning tips, end mills, drills, and broaches, as well as wear resistance and seizure resistance It can be applied to the tools for precision plastic working required.

Claims (7)

[Claims] 1. A coated hard tool formed by coating a hard coating layer by an ion plating method and using a super-hard alloy such as high-speed steel, cemented carbide, or cermet as a base material, at least a part of the hard coating layer, _(Ti x _{Al 1-x)}
A first layer of N (0.2 ≦ x ≦ 0.5) and (Ti _x Al)
_{1-x) O y N 1} -y (0.5 ≦ x ≦ 0.7,0.01
≤ y ≤ 0.5), wherein the second layer has a crystal continuity with the first layer in contact with the second layer. 2. The coated hard tool according to claim 1, wherein
A coated hard tool coated with an Al oxide layer, oxynitride layer or oxycarbonitride layer as an outermost layer. 3. The coated hard tool according to claim 2, wherein
A coated hard tool, wherein the outermost Al oxide layer, oxynitride layer or oxycarbonitride layer has an amorphous crystal structure. 4. The coated hard tool according to claim 2, wherein
A coated hard tool, wherein the outermost Al oxide layer, oxynitride layer or oxycarbonitride layer is crystalline. 5. The coated hard tool according to claim 1, wherein the thickness of the second layer to be laminated is 2 nm or more and 100 n.
m or less. 6. The coated hard tool according to claim 1, wherein a part of the metal component of the first layer and / or the second layer is contained in the range of 1 to 30 atomic% in the range of Si, Y, Nd and Sm. A coated hard tool, wherein one or more of Sc is replaced. 7. The coated hard tool according to claim 2, wherein the metal component of the outermost layer has a T content of 1 to 30 atomic%.
A coated hard tool characterized by being replaced by one or more of i, Si, Y, Nd, Sm, Sc.